This invention relates to propellants and more particularly to energetic nitramine plasticizers for propellants.
In 1974 several energetic nitramines were disclosed as potentially useful as energetic plasticizers for propellants. 2,4-dinitro-2,4-diazapentane (commonly called dimethylmethylene dinitramine or DMMD) appeared to be the most promising of those candidates. However, its effect on the ballistic properties of a double base or composite propellant could not be evaluated because of the difficulty and costly process involved in preparing larger quantities of it. The literature procedure can be summarized as follows: ##STR1## Kazuo Shiino and Senzo Oinuna, Kogyo Kayaku Kyokaishi 21, 351-7 (1960), disclose steps (1) and (2) of the process (see Chemical Abstracts volume 55, column 23340). The proceduure requires the isolation and purification of N,N'-Dimethyl-N,N'-dinitrourea (DMDU) in step (1) prior to its hydrolysis in step (2). DMDU in isolated form is a unstable, energetic explosive (at least one accidental explosion has occurred). Additionally, the yield of DMDU is rather low. The hydrolysis of DMDU (step 2) is not reported in detail; however, of the isolation and purification of the product methylnitramine (MNA) is rather time consuming. Step (3) of the procedure was disclosed by Leon Goodman, in "Condensations of Primary Aliphatic Nitramines with Formaldehyde," J.A.C.S. 75, 3019 at 3020 (1953). Step 3, a condensation reaction between paraformaldehyde and 2 molecules of MNA, requires a huge excess of concentrated sulfuric acid (for depolymerization of paraformaldehyde and dehydrating of MNA) which is definitely impractical and economically not feasible for large-scale process.